1. Field of the Invention
The present invention relates to vulcanizable compositions based on elastomeric copolymers of vinylidene fluoride, a process for vulcanizing such compositions and the vulcanized compositions obtained thereby.
2. The Prior Art
Vinylidene fluoride copolymers based on vulcanized elastomers are quite well known and are widely used in fields where exceptional chemical resistance to solvents, lubricants, fuels, acids and other like products is required, even at very high temperatures.
The vulcanized articles obtained from such heretofore known elastomeric copolymers are most suited for use in the field of sealing gaskets used under both static and dynamic conditions, in the motor-engineering field, in the aeronautical field, in shipbuilding, in the mechanical field, in the chemical field, in protective waterproofing of various supports, such as protective clothing against contact with aggressive chemical agents, sheaths for electrical cables exposed to heavy thermal radiation and, finally, as protective coatings on industrial containers and vessels.
According to the prior art, in the vulcanization of elastomeric vinylidene fluoride copolymers, there are used as vulcanizing agents, polynucleophilic compounds, and more particularly, polyhydroxy, aromatic compounds (or similar thiol-derivatives), as such and in the form of salts.
These known products yield vulcanized articles having satisfactory physical-mechanical characteristics and satisfactory thermal resistance.
Such products have, however, the disadvantage of requiring extremely long vulcanizing times, and thus, their practical utilization as vulcanizing agents is effectively prevented.
On the other hand, if, in order to reduce the vulcanization time, one attempts to increase the quantity of such vulcanized compounds, one would, of course, attain a higher vulcanization rate, but at the same time the characteristics of the final vulcanized products would be unacceptable; and thus, the practical utilization of the manufactured articles would again be effectively prevented. It is an object of the present invention to avoid the above disadvantages of the known products.